A line is an identifiable path created by a point moving in space. It is one-dimensional and can vary in width, direction, and length. Lines often define the edges of a form. Lines can be horizontal, vertical, or diagonal, straight or curved, thick or thin. They lead your eye around the composition and can communicate information through their character and direction.
Horizontal and vertical lines used in combination communicate stability and solidity. Rectilinear forms with 90-degree angles are structurally stable. This stability suggests permanence and reliability.